How do size and weight influence shipping costs?

Shipping costs are influenced by both the size and weight of the package, with heavier packages generally incurring higher costs due to the additional handling, transportation, and resources required to move them. In shipping, costs are typically calculated based on dimensional weight, which considers both the weight and size of the package. Carriers often use the greater of the actual weight or the dimensional weight when determining shipping rates. This means that as the weight of a package increases, it not only increases the physical demand on the shipping carrier's resources but also may require different handling considerations. Therefore, heavier packages can lead to higher shipping fees as they present more challenges in transportation compared to lighter items.

In contrast, the other options do not accurately reflect how shipping costs work. Some may suggest that larger items could lead to lower costs, but in reality, size and weight both contribute to the overall cost structure. Stating that size and weight have no effect is also incorrect, as they are critical factors taken into consideration during shipping calculations. Moreover, saying that only dimensions matter overlooks the significant influence that weight has on shipping logistics and costs.